This invention relates to the field of nonlinear electronic processing of light image data collected by an optical viewing system; light in this context is meant to include electromagnetic energy in the ultraviolet, visible and infrared spectral ranges.
Optical systems having electrical output signals are employed in object detection, television, pattern recognition, and other present-day electronic systems. Usually in these systems a small area light to electrical transducer element is exposed to a precisely defined portion of the incident radiation in order to provide an electrical signal which represents a small area in a viewed scene. Exposures of this type are repeated a plurality of times in either a parallel or serial exposure arrangement to obtain a complete electrical representation of the viewed scene. In many such present-day systems, it is common to transmit the electrical signal from an exposed transducer over a considerable distance before performing initial electrical signal processing operations.
Some modern military optical-electronic systems are finding it desirable to combine these optical sensing and initial electronic signal processing operations into a single module of considerably increased capability in comparison with prior sensor and initial processing devices. Modules of this type are frequently constructed on an integral circuit substrate which is used both to contain the electronic processing circuitry and to support the optical transducer array. Such arrangements are found to be especially useful in smart weapons such as guided missiles and bombs where the module characteristics are also dictated by a combination of small physical space, strenuous physical environment, nonlinear electrical properties and nontaxing image quality requirements. A discussion of the sensor needs and combination optic and transducer arrangements appropriate for such weapons is contained in my above referenced and copending first and second patent applications, Ser. Nos. 475,676 and 555,803, respectively. The disclosure of these two applications is hereby incorporated by reference into the present specification.
The U.S. Patent art includes examples of nonlinear signal processing systems of the separate sensor and processing type used for a variety of purposes. One such prior patent, U.S. Pat. No. 3,313,939, is issued to Herbert C. Spencer of Taplow, England and concerns an apparatus which senses the amount of sunlight received by garden plants in order that a correlation between sunlight dosage and artificial watering of the exposed plants be achieved. The Spencer invention includes electronic processing of optically generated electrical signals and includes the accummulation of an electric charge representing sunlight intensity and duration on a capacitor element together with the concepts of discharging the capacitor upon attainment of a predetermined voltage and counting the number of discharge occurrences in a predetermined time interval. In the Spencer invention plant watering is commenced upon attainment of a preselected number of capacitor discharge events.
The Spencer apparatus employs separate light-sensing and electronic processing structures and is limited to a single channel of optical and electronic signals. The light sensor in this apparatus is a conventional device of the planar solar cell variety. The Spencer apparatus is unconcerned with the rate of information accummulation or the mathematical relationship between input radiation rate and the time of attaining water valve turn-on, that is, with the input to output algorithm achieved in the electronic signal processing. The Spencer apparatus is, of course, concerned with long-time intervals and employs correspondingly large electrical components of the discrete component type in achieving the light signal processing. The possibilities of integrated circuit fabrication, numerous signal processing channels, and nonlinear input-to-output relationship as might be required in an imaging system is not considered in the Spencer patent.